A. Iwata

Aircraft measurements of oxides of nitrogen along the eastern rim of the Asian continent: Winter observations

Aircraft observations of oxides of nitrogen (NOy), measured with a ferrous sulfate converter, over the sea surrounding the Japanese islands (30–43° N, 131–141° E) were carried out in the winter of 1983 and 1984 at altitudes mostly between 3 and 8 km. NOy defined here is the sum of NO, NO2, and other unstable oxides of nitrogen that are converted to NO by ferrous sulfate. The main observations were:(1)Over the Pacific Ocean between the latitudes of 30–35° N, the observed NOy mixing ratio between 3 and 8 km was a fairly constant 200 pptv. The NO mixing ratio increased with altitude from 15 pptv at 3 km to 35 pptv at 7 km.(2)Over the Sea of Japan, tropospheric NOy mesured between 1 and 6 km started increasing with latitude North of 35° N and reached about 1000 pptv at 40° N.(3)NOy was measured in an air mass transported from the stratosphere near a tropopause fold region. When the ozone mixing ratio was between 80 and 140 ppbv, the NOy mixing ratio was about 200 pptv.

Balloon‐borne chemiluminescent sonde for the measurement of tropospheric and stratospheric nitric oxide

A new chemiluminescent sonde for the balloon‐borne measurement of nitric oxide has been developed. Air is drawn through the reaction chamber by a constant volume pump with a volume flow rate of approximately 300 l/min essentially independent of the altitude, and mixed with ozone, generated on board by silent discharge from pure oxygen. The flow of the ozone/oxygen mixture is regulated at a constant flow rate of 400 STP cm3/min by a mass flow controller. To calibrate the system sensitivity periodically in flight, NO in N2 gas, with a concentration of 2 ppm, is injected at the inlet tube with flow rates of 9 and 18 STP cm3/min controlled also by a mass flow controller. Teflon coated internal surfaces have allowed the instrument to have a quick response and this has led to reliable measurements of NO at low mixing ratios. The overall accuracy in determining the NO mixing ratio is between 5% and 10% depending on the altitude, and the detection limit is 10–20 ppt.

Measurement of Oxides of Nitrogen in the Free Troposphere over Japan

Aircraft observations of NOx(NO and NO2) over the sea surrounding the Japanese islands(30–43°N, 131–141°E) were carried out in the winter of 1983 and 1984 at altitudes between 3 and 8 km. The main NOX features observed are as follows: 1) Over the Pacific ocean between the latitudes of 30–35°N, the observed NOX mixing ratio at 3–8 km is fairly constant at 0.2 ppb. The NO mixing ratio increases with altitude from 20 ppt at 3 km reaching 40 ppt at 7 km. 2) The NOx mixing ratio measured in the air mass transported from the stratosphere was also about 0.2 ppb. 3) Over the sea of japan, the tropospheric NOx mixing ratio starts increasing with latitude North of 35°N and reaches about 1 ppb at 40°N.

Nitric oxide profile from 7 to 32 km

Within the framework of the MAP-Globus campaign, a chemiluminescent NO detector was launched, together with a similar experiment from the Max Planck Institut fur Aeronomie, Lindau, West Germany on September 20, 1983 from Aire sur l’Adour, France,(44°N, 0°W). The balloon was piloted to perform an excursion from 32 km to 22 km during the flight and returned to float at 32 km one hour before sunset to enable a sunset study to be made. The first ascent profile showed a rapid increase in NO mixing ratio from 50 ppt at 7 km to 250 ppt at the tropopause indicating a downward transport of NO into the troposphere. The nitric oxide mixing ratio continued to increase to be about 1 ppb at 25 km, and increased even more rapidly above 25 km to reach a value of approximately 10 ppb at 32 km. The first ascent and descent profiles, obtained with a SZA of less than 57° coincided even in detail to within 5% between 22 and 32 km assuring instrumental precision. The unchanging NO mixing ratio during the day is indicative of a very low mixing ratio of N2O5 compared to N0x, at least at mid-latitudes. The NO concentration at 32 km gradually decreased from when the SZA was 70° to sunset at which time it rapidly decreased by more than an order of magnitude in 10 minutes.